356 
MR.  R.  OWEN  ON  THE  OSTEOLOGY  OF 
In  the  course  of  this  comparison  it  will  be  shown  that  the  number  and  value  of  the 
points  of  resemblance  or  of  approximation  to  the  Bimanous  structure  are  in  favour 
of  the  Chimpanzee ;  and  that,  as  in  many  similar  instances,  there  are  some  particulars 
of  the  organization  of  the  Orang  which  indicate  a  closer  affinity  with  the  inferior  forms 
of  the  group  to  which  it  belongs  than  to  those  Quadrumana  which  rank  immediately 
below  it. 
Notwithstanding  the  many  strongly  marked  characters  which  the  cranium  of  the  adult 
Orang  exhibits  in  common  with  that  of  the  Mandrill,  as  the  contracted  forehead,  the 
flattened  occiput,  the  formidable  canine  teeth,  huge  jaws,  strong  expanded  zygomatic 
arches,  and  largely  developed  cranial  ridges,  yet  in  continuing  the  comparison  we  can- 
not fail  to  be  struck  with  the  general  effect  of  a  less  ferocious  expression  in  the  skull  of 
the  Orang.  This  results  from  the  more  perpendicular  slope  of  the  facial  contour,  from 
the  absence  of  the  projecting  superciliary  ridges  (beneath  which  even  the  sightless 
sockets  of  the  Mandrill  scowl  upon  the  observer),  from  the  greater  expansion  of  the 
cerebral  cavity,  and  lastly,  from  the  non-development  of  the  superior  maxillary  ridges, 
which  appear  in  the  Mandrill  as  a  gratuitous  supplement  to  the  hideous  tout  ensemble  of 
its  head. 
The  cranium  of  the  Orang  is  less  flattened  at  the  crown  than  that  of  the  Chimpanzee. 
The  size  of  the  cavity  of  the  skull  exceeds  in  a  very  small  degree  that  of  the  young 
animal  at  the  period  when  it  has  acquired  the  first  permanent  molares,  the  subsequent 
enlargement  of  the  cranium  being  chiefly  owing  to  the  thickening  of  its  walls  and  to  the 
development  of  the  muscular  ridges  which  circumscribe  the  origins  of  the  temporal  mus- 
cles. These  ridges  commence  at  the  external  angular  process  of  the  frontal  bone,  pass 
inwards,  upwards,  and  backwards  behind  the  superciliary  ridge,  from  which  they  are 
separated  by  a  deep  groove,  then,  converging  upon  the  cranium,  they  meet  at  the  junc- 
tion of  the  sagittal  with  the  coronal  suture,  including  a  neat  triangular  portion  of  the 
frontal  bone,  along  the  middle  of  which  there  is  a  slight  longitudinal  convexity.  The 
smoothness  of  this  part  of  the  cranium  forms  a  contrast  to  the  irregularly  indented  sur- 
face of  the  remainder,  which  is  exclusively  the  seat  of  origin  or  attachment  of  powerful 
muscles. 
The  interparietal  crest  rises,  as  in  the  Hyand  and  other  Carnivora,  above  the  ge- 
neral level  of  the  skull,  to  the  extent  of  from  -f  to  -§-  of  an  inch ;  at  the  vertex  it  divides 
and  passes  posterior  to  the  lambdoidal  suture  to  the  mastoid  ridge.  A  third  strong 
spine  is  continued  from  the  point  of  divarication  half  way  down  the  squamous  portion 
of  the  occiput,  and  forms  a  strong  posterior  projection  at  its  commencement.  The 
situation  of  these  ridges  in  reference  to  the  sutures,  is  only  determinable  by  comparing 
the  faint  commencement  of  their  growth  in  the  young  Orang's  skull.  In  two  adult 
skulls,  where  the  ridges  were  fully  developed,  the  only  traces  of  the  cranial  sutures 
which  were  visible  were  the  upper  part  of  the  squamous,  about  1  inch  of  the  lower 
end  of  the  coronal,  and  that  small  one  by  which  the  ala  of  the  sphenoid  joins  the 
